• Tunnel and Underground Space
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• v.13 no.3
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• pp.225-234
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• 2003

The structures to be demolished have become diverse in types from reinforced concrete to steel. The demand for demolition of steel structures is recently increasing in Korea. Most of flexible linear-shaped charges for steel demolition are now imported from foreign countries. To determine the optimum parameters of design far domestic development of flexible linear-shaped charges, some basic experiments have been carried out and their results are summarized as follows; Copper is shown to be superior to aluminium and lead as a liner material. It is also proved that the optimum apex angle of liner is 90$^{\circ}$ in comparision with 45$^{\circ}$, 60$^{\circ}$ and 120$^{\circ}$ Adequate thickness of liners, standoff distance in terms of quantity of explosives are also examined. Explosives and liners are required to be plasticized in order to improve the bond between explosives and various shapes of steel structures.

• Tunnel and Underground Space
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• v.10 no.4
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• pp.516-525
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• 2000

Recently, the demand for pollution-free demolition work of old reinforced concrete and steel structure has rapidly increased as the redevelopment of urban area has been accelerated. This study deals with linear shape charges for explosive jet cutting on steel structure. We have tested material and shape of steel structure, characteristics of thickness and strength, shape of linear shape charges, type of shape charges, cumulative charges, type of liner, stand-off distance, detonation method. effect of sound and vibration by air blast in explosive jet cutting method. So, We developed linear shape charges in order to take advantage of optimum explosive jet cutting condition. Shape charges were made of PETN explosives. We obtained the experimental formula to decide the amount of explosive needed for thickness of steel structure plate. There are prospects for application of the explosion curving technology under the open space conditions for dismantling the steel structure and steel bridge, scrapped old boats, which are going out of service.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.10
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• pp.3988-3997
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• 2010

Shotcrete was a mortar or concrete that is pneumatically projected at high velocity onto a subject. It has been applied for tunneling, underground big-spaces, slope stabilization. Shotcrete is increasing use in structure repair. The dry-mix shotcrete require a smaller equipment, easy maintenance, possible of very-earlystrength materials than wet-mix shotcrete, which make this process attractive and economic for structural repairs. It is common practice core compressive strength to the dry-mix shotcrete quality control. This test is very difficult estimating eraly-strength of Very-Early-Strength Dry-Mix Shotcrete. The purpose of this research was to analyze the correlation of test results among cube test, core test, pullout test and maturity. The correlationship analysis of test results among cube test, core test, pullout test and maturity showed more than 90%.

• International Journal of Highway Engineering
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• v.16 no.5
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• pp.155-164
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• 2014

PURPOSES : The purpose of this article is to compare and evaluate the riding comfort of a passenger in tunnels depending on different surface textures of concrete pavement. METHODS : Evaluation of riding comfort is conducted at 17 sections, which have different surface texture such as transverse tinned(TT), longitudinal tinned(LT) and diamond grinded(DG). A triaxial accelerometer was set up on the passenger seat surface of the test vehicle to measure vibrations of an occupant, then the effects of vibration on comfort and health were evaluated by ISO 2631. And microphones were installed at passenger's ears height to measure sound pressure level(SPL) in the test vehicle. Additionally, a surface microphone was installed on the inside of wheel arch to evaluate noise between tire and pavement by NCPX method. All tests were conducted cruising at 100km/h. RESULTS : The results of all tests are as follows. First, both vibration magnitudes for comfort and for health in LT and DG sections are almost same and they represent lower than those in TT sections. Second, the average SPL of DG shows the lowest decibels among them. And third, it is founded that interior noise is significantly affected by noise between tire and pavement. CONCLUSIONS : It may be concluded that DG can provide more excellent riding comfort to passenger than LT or TT. Therefore, it is necessary to consider applying DG to existing pavement surface to improve surface condition when the driving environment especially requires riding comfort like a long tunnel.

• Tunnel and Underground Space
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• v.16 no.5 s.64
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• pp.405-412
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• 2006

It is well known that shotcrete is the most important support member for the construction of large underground spaces. Generally, the strength of the field shotcrete is heavily dependent on the field mixing and spraying conditions so that it is different from the strength of the shotcrete mixed in laboratories. As a support member, the early strength of shotcrete unlike concrete is very important to the initial stabilization of the underground spaces. Therefore, the field methods to efficiently test the early strength of shotcrete have been highly required. This paper aimed to verify the pneumatic pin penetration test and the point load test for measuring the early strength of the field shotcrete. As a result of the experiments through a series of uniaxial compression, pin penetration, and point load tests for the range of the early shotcrete strength, two equations to estimate reliably the uniaxial compressive strength by the pin penetration and the point load tests were acquired.

• Journal of Korean Society of societal Security
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• v.3 no.1
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• pp.43-50
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• 2010

Sliding accidents on the road have a high percentage by road freezing, especially, they often have appeared at bridges and Tunnel of freezing areas. Thus, the stability of road operations is enhanced by preventing partial freezing phenomenon. According to the geothermal snow melting system analysis, a pattern of thermal conductivity is found out; pavement materials of concrete and asphalt where the system is buried. The heat transfer simulation is essential when the geothermal snow melting system is applied according to heating exchanger pipe placed in the lower pavements. The model tests are conducted on low temperature in freezer using the manufactured test model which is equal to pavement materials. Many variables are discovered from numerical analyses under the same conditions with model test.

• Explosives and Blasting
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• v.21 no.2
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• pp.21-30
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• 2003

Currently, the shotcrete used as basic support in the tunnel excavation, has the advantages of maintaining high-level strength in condition of early shooting with thin thickness based on the excavation characteristics of rock mass. Therefore supreme equipment and materials were developed and the great strides have continued. Also, the development of measurement technology and the rocks behaviors of undergound are evaluated in detail and the designs of strength and thickness are made. The reinforcement materials development of new material is carried on. Most of the coal fly ash produced in Korea fire power plant is fly ash and bottom mash. Fly ash has been producing to be applied in many fields such as cement, aggregate, construction, civil, agriculture and fisheries. Also a lot of experiments are actively on the way. Therefore in this experiment, in order to use the fly ash mixed with concrete as a material of shotcrete, the experiment was performed in the best content to reduce the compression strength and the shooting rebound ratio of the excavated surface to use fly ash as a substitute material of concrete. As a result, when 15%.wt substitution was made to the fly ash, about 10% of compression strength and 6% of rebound ratio was reduced.

• Journal of the Korean Geotechnical Society
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• v.28 no.8
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• pp.79-88
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• 2012

In this study, the tunnel loads acting on the concrete lining are analyzed by comparing three methods - Terzaghi table, Terzaghi formula and Ground-Lining Interaction (G.L.I) model. The tunnel loads are analyzed by FLAC 2D. And the G.L.I model is analyzed under various rock mass ratings, tunnel depths (20~80m) and in-situ stress ratios ($K_0$=0.5~2.0). Terzaghi's method can be applied only to weathered rocks and soils, and cannot reflect the effect of various tunnel depths and in-situ stress ratio. The proposed G.L.I model can not only be applied to various ground conditions, but also relieves the tunnel loads by up to 30%.

• Journal of the Korean GEO-environmental Society
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• v.9 no.5
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• pp.29-36
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• 2008

The shotcrete is a NATM technique as a major tunnel support for ground stability after tunnel excavation. Instead of a general concrete lining method, it is a trend for curtail of construction periods and reduction of construction expenses that required to use of the permanent shotcrete lining. This high-strength shotcrete is required to use as a permanent shotcrete lining. This brought out the solution of environmental pollution and harmfulness to human. Accordingly, in this study specimens for strength measurement were made to develop shotcrete possible to develop materials in early with cement mineral accelerator as NATM method construction. It was compared with existing shotcrete material, unconfined compression test, flexural strength test, antiwashout underwater test were experimented. The fish poison test was experimented to evaluate an influence of environment. As a results of the test, unconfined compressive strength and flexural strength were equivalent with 28-curing day strength of existing material. An antiwashout of research subject material was revealed excellently in antiwashout Underwater test. As a results of the fish poison, an evaluation research subject material was founded more environmentally friendly than existing shotcrete.

• Geophysics and Geophysical Exploration
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• v.2 no.4
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• pp.174-179
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• 1999

Shear wave velocity, one of major elastic constants in the dynamic design for civil structures, is conventionally measured from downhole, crosshole or sonic logging tests. SASW (Spectral Analysis of Surface Waves) method, which overcomes the disadvantage of the in-hole tests, can evaluate subsurface stiffness nondestructively and nonintrusively through measuring surface waves on surface. In this paper, principles of the SASW method are briefly described and the results of various field tests, conducted to investigate the applicability of the method, are summarized. The SASW method was successfully applied in evaluating the effects of dynamic compaction at Inchon international airport site, applied in evaluating the integrity of the lining and sidewall at a testing tunnel located in Mabukri, and applied in detecting thickness of a concrete retaining wall. The results of field tests and the nondestructive and economical characteristics of the method show the promising future of the SASW method in civil engineering projects.